Render different frames
Here's a quick script to render out separate frame ranges of the animation. The script assumes you've set an output folder correctly as well as setting the video format settings as you want them.

import bpy
import os

frameList = [
    [1,50],
    [51,100],
    [101,150]
    ]

scn = bpy.context.scene

for fr in frameList:

    scn.frame_start = int(fr[0])
    scn.frame_end = int(fr[1])
    bpy.ops.render.render(animation=True)